1. Field of the Invention
The present invention generally relates to digital cameras. More particularly, improved digital camera architectures and components are described.
2. Description of the Related Art
Recently, digital cameras have become very popular. The digital camera converts an optical image to electronic image data and digitally records the image data on a storage medium. When the image is reproduced, the recorded digital data is retrieved from the storage medium and displayed on a display device or printed out as a hard copy image.
Referring initially to FIG. 1, conventional digital camera systems 100 typically include a digital camera 102 having an optical lens 104 for focusing light rays onto an imaging capture unit 106. The imaging capture unit 106 typically relies upon an array of light sensitive photo optic cells 108, capable of converting the light rays received from the optical lens 104 into representative analog signals. Most commonly, the photo optic cells take the form of charge-coupled devices (CCDs), although other devices such as CMOS receptors may be used as well. As is well known in the art, each CCD array 108 must have associated with it a specific color filter array (CFA). In most applications, the CFA is an empirically derived pattern of individual color filters each associated with a specific CCD cell in the CCD array. A color converter circuit 110 then uses a particular interpolation algorithm associated with the specific CFA to generate the analog signals representing the CCD manufacturer""s predetermined concept of the proper color scheme of the image. Manual input controls 103 (i.e., push-buttons, for example) provide manual inputs to a step controller 105 suitably disposed to provide control signals to the imaging capture unit 106. Such control signals are used to control such imaging parameters as f-stop, exposure, zoom, focus, and flash attachments, if appropriate.
The imaging capture unit 106 sends the analog signals representing the image first to an analog-to-digital (AID) converter unit 112. The A/D converter unit 112 converts the representative analog signals into digital signals representative of the image. The digital signals are then passed to a digital signal processor (DSP) 114 where they are converted to appropriate digital formats. An image compression circuit 116 as well as a memory 118 both receive the appropriately formatted digital signals. The image compression circuit 116 operates to digitally compress the received digital images in order to -reduce the amount of resources required to further process the digital signals. One such formatting scheme referred to as JPEG is commonly used, although there are a wide variety of suitable picture formats. Once the image has been digitally compressed, it is sent by way of a memory interface 120 to a memory slot 122 capable of receiving a memory card 124 suitable for storing the compressed digital signals. Such memory cards 124 include xe2x80x9cfloppyxe2x80x9d disks, flash EPROM cards, R/W compact disc (CD), SmartMedia and the like.
Unfortunately, conventional digital cameras have several important limitations. One such limitation is the fact that the conventional digital camera may only use the color filter array (CFA) and its associated color interpolation algorithms. Any subsequent improvements in CCD array technology cannot easily be incorporated into the conventional digital camera system.
Lack of integration also provides for expensive and cumbersome digital cameras. As can be readily seen, the conventional digital camera system 100 has many discrete functional blocks encompassing many different circuits. It is therefore relatively expensive for conventional digital cameras to provide image correction, color correction, image compression, as well as provide all appropriate control and timing signals in one unit.
In addition, each CCD or CMOS imager has different clocking requirements, resolution, etc. That requires dedicated ASICs, or other dedicated logic, to properly drive them. This results in higher manufacturing cost and an inflexible camera architecture.
It would be advantageous and therefore desirable to have available components that can be used by a variety of digital camera manufacturers, regardless of their specific image sensor, color interpolation scheme, etc.
Digital cameras and methods for using digital cameras that are capable of authenticity stamping captured images are disclosed. In one aspect, the digital camera includes an image capture unit arranged to output analog signals that represent a captured image. The digital camera also includes a converter unit for converting the analog representations of the captured image to a digital representation of the image and an image processor arranged to create an image file from the digital representations of the image. The digital camera further includes an authentication stamper for inserting authentication stamps in the image file.
In another aspect of the invention, a method of authentication stamping a digital image is disclosed. In this embodiment, an authentication stamper attaches to the captured image information useful in authenticating the source of the captured image. The captured image is authenticity stamped within the digital camera by attaching to the captured image information useful in authenticating the source of the captured image.
In one preferred embodiment, an image digest, which is a function of the captured image and identification information that is useful in authenticating the source of the captured image, is created. In some implementations, the image digest is formed using a one-way HASH algorithm, and the encrypting is done using a secure key that is a private key.
In yet another aspect of the invention, a method is disclosed for authenticating the source of a digital image that has an authentication stamp that has been attached to the image by a digital camera that originally captured the digital image. A first image digest is formed from the digital image being authenticated. A second image digest is created from the attached authentication stamp. Finally, the first image digest is compared to the second image digest to determine whether the first image digest and the second image digest are the same. When the first image digest and the second image digest are the same, the source of the digital image is considered to be authenticated.